1. Field of the Invention
The present invention is directed to an improved process for the activation of iron containing catalysts and, more particularly, to the activation of iron catalysts which are especially adapted to the hydrogenation of adiponitrile to hexamethylenediamine.
2. Description of the Prior Art
The catalysts to which the process of the present invention is applied are described throughout the art and particularly in U.S. Pat. No. 3,696,153 issued on Oct. 3, 1972 which patent discloses the hydrogenation of adiponitrile at elevated temperatures and pressures in the presence of a catalyst derived from an iron compound, e.g., iron oxide, in granular which catalyst has been activated with hydrogen at a temperature not exceeding about 600 .degree. C. An improved process for activating the iron oxide hydrogenation catalyst for use in a similar reaction by employing a mixture of hydrogen and ammonia for activation at a temperature in the range of about 300.degree.-600 .degree. C. is disclosed in U.S. Pat. No. 3,758,584 issued on Sept. 11, 1973.
The use of a fused and solidified iron oxide catalyst containing at least 96.5% iron oxide and having an atomic ratio of oxygen to iron of 1.2:1-1.4:1 for the hydrogenation of adiponitrile to hexamethylenediamine is disclosed in U.S. Pat. No. 4,064,172 issued on Dec. 20, 1977.
U.S. Pat. No. 3,986,985 issued on Oct. 19,1976 discloses a technique for stabilizing an iron containing catalyst to render it nonpyrophoric which technique involves treating the catalyst with a gas having a low oxygen content, e.g., air diluted with nitrogen. This treatment is taught to produce a surface coating which is stable and nonpyrophoric and thus a catalyst which is stable. The patentees disclose that the catalyst activity may be restored by a short treatment with hydrogen.